Increased incidence of fractures and bone pain are major public health problems for elderly women. Bone loss is a major factor in these problems, but the mechanisms responsible are not clear. Classic senile or postmenopausal osteoporosis may be a concomitant of the normal aging process, or a disease affecting only a fraction of the aging population. Retrospective, cross sectional studies of relative skeletal status have not answered this question. Longitudinal studies of fractures in the elderly as related to subjective interpretation of spinal roentgenograms have not clarified the situation either. Our laboratory is investigating methods for objectively evaluating skeletal status. We will apply 2 of the methods: Bone mineral determination by monoenergetic photon absorptiometry and measurement of bone resonant frequency. We will finish the protocol involving repeated measurements of mineral content and resonant frequency of various sites in the appendicular skeletons of 200 normal women over a period of 2 years. The women were about 35 to 55 years of age at the beginning of the study and received physical examinations and laboratory tests (blood and urine chemistries) to rule out existence of conditions such as hyperparathyroidism, rheumatoid arthritis, etc. which may have generalized skeletal manifestations. This study will show: (1) Individual rates of bone loss as a function of age, height, weight, parity, etc.; (2) Whether a distinct subpopulation with a relatively rapid rate of bone loss exists; (3) Whether changes in bone rigidity (resonant frequency) precede changes in bone mineral (suggesting an alteration of bone quality), or whether the 2 changes occur simultaneously (suggesting simple changes in bone mass) and (4) Normative values of skeletal condition in women based on objective measures of skeletal status.